Kaplan Nursing Entrance Practice Exam

What constitutes active immunity in the immune system?

1. Physical barriers to infection

2. Cellular components including white blood cells

3. Antibodies in the bloodstream

4. Stored memory cells

The correct answer is: Cellular components including white blood cells

Active immunity is primarily characterized by the immune system's response to pathogens, where the body actively produces antibodies and engages various components of the immune system to combat infections. The correct answer emphasizes cellular components, particularly the role of white blood cells, which are crucial in recognizing and responding to pathogens. When the body encounters an infectious agent, specific types of white blood cells, such as T cells and B cells, are activated. B cells are responsible for producing antibodies that specifically target the pathogen, while T cells help regulate the immune response and can directly kill infected cells. This process involves a memory component, meaning that the immune system can "remember" the pathogen for future exposure, allowing for a quicker response during subsequent infections. The other choices provide components of the immune system or factors related to immune response but do not capture the essence of active immunity as effectively. For instance, physical barriers (like skin and mucous membranes) serve as the first line of defense but do not involve the immune system's active response. Antibodies in the bloodstream reflect a result of the immune response but do not illustrate the active participation of the immune system during the initial encounter with a pathogen. Lastly, stored memory cells are a product of a successful immune response but do not encompass the